Display devices are important for many kind of electronic equipment and customer devices. The technical development in this field focuses amongst others on processes and devices for illumination, image generation and projection. It is, however, a well-known problem that illumination devices may loose a significant amount of primary produced illumination light because of an insufficient adaptation between for instance a broad band light source and respective spectral splitting devices or the like. On the other hand, it is also known in the art that illumination devices and respective light sources do not only generate light in a desired spectral channel with respective profiles and distributions of the generated radiation but also tend to inherently produce some parasitic or optical noise which is known in particular as speckles in colour image displays using coherent, e.g. laser light sources.